Fifty-five boys and 61 girls, aged 5-16 years, took part in a 15-week longitudinal study of stress and upper respiratory infectious illness. Life events, social support, and psychological coping were measured, and hassles and mood were assessed repeatedly throughout the study period. Upper respiratory symptoms were recorded daily, and episodes of upper respiratory infection were verified by clinical examination. Forty-eight verified episodes of infection were recorded from 41 participants (35.3% of the total sample). Life events and social support interacted in predicting the occurrence of infection, whereas hassles interacted with avoidant psychological coping, independently of age, gender, family composition, social class, negative affect, parental perceived stress, parental smoking, or alcohol consumption. The duration of symptomatic episodes was negatively associated with problem-focused coping, and positively related to avoidant coping. Hassle levels were elevated 3 weeks prior to symptom onset. These results indicate that the impact of life stress on vulnerability to infectious illness in children is moderated by psychological coping and social resources, and that different psychosocial factors influence the occurrence and duration of infections.